1. Field of the Invention
The present invention relates to a honeycomb structural body and a die for forming the honeycomb structural body by extrusion. More particularly, the present invention relates to a honeycomb structural body suitably used as a filter for collecting fine particles in exhaust gas from internal combustion engines, boilers, and the like or as a filter for liquids in water supply system, sewerage system, and the like, while controlling an increase in the pressure loss during use, and to a die capable of easily forming such a honeycomb structural body by extrusion.
2. Description of Background Art
In view of the effects on environment, necessity for removing fine particles and toxic substances from exhaust gas of internal combustion engines, boilers, and the like has been increasing. In particular, regulations on removal of particulates from diesel engines are showing an intensified trend in the U.S., Europe, and Japan. A honeycomb filter utilizing a honeycomb structural body to collect particulates (hereafter called a diesel particulate filter or DPF) is used. The honeycomb filter utilizing a honeycomb structural body is also used for filtering liquids in water supply and sewerage systems (see JP-A-4-301114)
As shown in FIGS. 14(a) and 14(b), the honeycomb filter used for such an objective generally comprises an inlet port end face 42 and an outlet port end face 44 for a fluid, a partition wall 32 extending from the end face 42 to the end face 44, and a number of cells 33a and 33b with a square cross-section divided by the partition wall 32 and penetrating from the inlet port end face 42 through the outlet port end face 44, wherein each of adjacent cells 33a and 33b are plugged at the opposite end face so that the inlet port end face 42 and an outlet port end face 44 have respectively in a checkerwise pattern as a whole. In the honeycomb filter 31 having such a configuration, since a fluid such as a gas and liquid flows into cells 33b opening in the inlet port end face 42, specifically the cells 33b plugged at the outlet port end face 44, penetrates through the porous partition wall 32 into the adjacent cells 33a which are plugged at the inlet port end face 42, specifically the cells 33a opening on the outlet port end face 44, and is discharged from the cells 33a. In this instance, the partition wall 32 serves as a filtration side and the collected matters are deposited on the partition wall 32.
However, when the honeycomb filter 31 using such a honeycomb structural body is used as a DPF and the like, if a large amount of deposits such as soot accumulate in the opening of the cells 33b on the inlet port end face 42, the open area on the inlet port end face 42 decreases or the opening is blocked resulting in an increase in the pressure loss of the honeycomb filter 31. The output of the diesel engine is lowered and the fuel consumption decreases.
The present invention has been completed in view of such a situation and has an object of providing a honeycomb structural body suitably used as a filter for collecting fine particles in exhaust gas from internal combustion engines, boilers, and the like or as a filter for liquids in water supply and sewerage systems while controlling an increase in the pressure loss during use, a filter structure utilizing such a honeycomb structural body, and a die capable of easily forming such a honeycomb structural body by extrusion.